Propylene oxide is an important industrial chemical intermediate. Propylene oxide can be produced by direct oxidation of propylene with oxygen and hydrogen in a solvent in the presence of a catalyst (U.S. Pat. Nos. 7,138,535 and 5,973,171). A buffer helps to improve the selectivity to propylene oxide (U.S. Pat. No. 6,498,259).
The copending application Ser. No. 11/588,453, filed Oct. 27, 2006, teaches an improved process for producing epoxide by catalytic reaction of olefin, hydrogen, and oxygen wherein the reaction is modified by the presence of buffer salts in the reaction mixture. The improvement comprises recovering the buffer by electrodialysis and/or crystallization and recycling the recovered buffer to the reaction.